1. Field of the Invention
The present invention relates to a cleaning agent for cleaning paint piping employed for coating automotive bodies and the like and a process for cleaning paint piping employing the same.
2. Description of the Related Art
FIGS. 1 and 2 show an example of paint piping employed for coating automotive bodies. A paint or coating is stored in a tank 1. When a hydraulic pump 2 shown in FIG. 1 is driven, the coating is circulated such that it may pass first through a filter 3 and then is pumped through a feed pipe 4 to a main piping 5 to be returned to the tank 1 through a return pipe 6, and a part of the coating in circulation is used for coating automotive bodies.
The main piping 5 is a pipe line for feeding the coating to a coating spot and has on the way branch pipes 7 connected thereto at predetermined intervals, as shown in FIG. 2. Each branch pipe 7 is formed by connecting a plurality of pipe units and has a regulator 12 provided at the middle and a spray gun 8 for injecting the coating attached to the distal end. Further, a sub branch pipe 10 is connected to the branch pipe 7 via a color change valve 9, and this sub branch pipe 10 is connected to a sub piping 11. The sub branch piping 10 is also formed by connecting a plurality of pipe units.
In such paint piping, aggregates of coating materials adhere on the internal wall surface of the piping in a long while. Such coating aggregates not only lower the pressure of injecting a coating but also are injected together with the coating to be deposited on the material to be coated, being causative of defective coating. In order to remove the aggregates, the paint piping must be cleaned.
According to the prior art cleaning process, the coating is extracted from all the members constituting the paint piping including the tank, the main piping, branch pipes, etc., and a cleaning thinner is circulated through the paint piping. However, it is impossible to remove the coating aggregates adhered stiff to the piping merely by circulating the cleaning thinner, and, in this case, the piping is cleaned using a special acidic cleaning agent based on a chlorine-containing solvent.
More specifically, while cleaning of the piping is carried out using an acidic cleaning agent containing a chlorine-containing solvent such as trichloroethylene, methylene chloride, tetrachloroethylene, 1,1,1,2-tetrachloroethylene and 1,1,2,2-tetrachloroethane, the piping must be disassembled to remove attachments such as the branch pipes 7, the sub branch pipes 10, the regulators 12 and the valves 9, since these attachments are difficult to clean. Accordingly, the pipe units constituting the main piping 5 having a large diameter are recombined into a form of straight pipe, and then a cleaning agent containing a chlorine-containing solvent is circulated through it and through the tank 1 to clean them.
The cleaning procedures employing such cleaning agent containing a chlorine-containing solvent are typically carried out as follows:
(1) A cleaning agent containing a chlorine-containing solvent at a high concentration of 80 to 90 wt % is circulated to clean the straight pipe and the tank; PA1 (2) The cleaning agent is extracted and is replaced with isopropyl alcohol (IPA) by circulating it; PA1 (3) A cleaning agent containing about 20 wt % of chlorine-containing solvent and an anti-corrosive is circulated to remove iron oxides, aluminum, etc.; PA1 (4) An alkaline solution containing sodium hydroxide and a chelating agent dissolved therein is circulated to effect neutralization; PA1 (5) A solution incorporated with a preservative is injected and then extracted; PA1 (6) IPA is circulated to remove moisture; PA1 (7) A cleaning thinner is circulated to remove IPA; and PA1 (8) A diluting thinner employed for diluting the coating is circulated to remove the cleaning thinner. PA1 (1) Since the chlorine-containing solvent is harmful, the cleaning is risky, and the greatest care must be taken in handling the solvent. The solvent if discarded causes environmental disruption; PA1 (2) The cleaning agent has strong acidity and corrodes the pipe, the pipe must be subjected to a reducing treatment, a neutralizing treatment and a preserving treatment after the cleaning procedures, making the post-treatment intricate; PA1 (3) Since a strong acidity solution and a strong alkaline solution are employed, the cleaning procedures involve risks; PA1 (4) Since the paint piping must be disassembled and the pipe units constituting the main piping must be recombined to form a straight pipe prior to cleaning, and since the paint piping must be reassembled after completion of cleaning, the cleaning procedures include many steps and require a long time (80 hours for achieving cleaning of a cleaning volume of 600 liters); and PA1 (5) Attachments excluding the main piping such as the branch pipes, the regulators, the color change valves, etc. cannot be cleaned. Accordingly, when the paint piping is reassembled, these attachment members must be replaced with new ones wastefully.
The prior art cleaning process described above involves the following problems: